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ntp: save PTP correction from NTP-over-PTP messages

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When the RX duration is known (HW timestamping), save the PTP correction
from received PTP messages in the local RX timestamp.
This commit is contained in:
Miroslav Lichvar 2023-09-26 12:22:47 +02:00
parent b0267475e3
commit 6372a9f93f
3 changed files with 19 additions and 6 deletions
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14
ntp_io.c
View file

@ -459,7 +459,7 @@ process_message(SCK_Message *message, int sock_fd, int event)
DEBUG_LOG("Updated RX timestamp delay=%.9f tss=%u",
UTI_DiffTimespecsToDouble(&sched_ts, &local_ts.ts), local_ts.source);
if (!NIO_UnwrapMessage(message, sock_fd))
if (!NIO_UnwrapMessage(message, sock_fd, &local_ts.net_correction))
return;
/* Just ignore the packet if it's not of a recognized length */
@ -498,8 +498,9 @@ read_from_socket(int sock_fd, int event, void *anything)
/* ================================================== */
int
NIO_UnwrapMessage(SCK_Message *message, int sock_fd)
NIO_UnwrapMessage(SCK_Message *message, int sock_fd, double *net_correction)
{
double ptp_correction;
PTP_NtpMessage *msg;
if (!is_ptp_socket(sock_fd))
@ -525,7 +526,14 @@ NIO_UnwrapMessage(SCK_Message *message, int sock_fd)
message->data = (char *)message->data + PTP_NTP_PREFIX_LENGTH;
message->length -= PTP_NTP_PREFIX_LENGTH;
DEBUG_LOG("Unwrapped PTP->NTP len=%d", message->length);
ptp_correction = UTI_Integer64NetworkToHost(*(Integer64 *)msg->header.correction) /
((1 << 16) * 1.0e9);
/* Use the correction only if the RX duration is known (i.e. HW timestamp) */
if (*net_correction > 0.0)
*net_correction += ptp_correction;
DEBUG_LOG("Unwrapped PTP->NTP len=%d corr=%.9f", message->length, ptp_correction);
return 1;
}

2
ntp_io.h
View file

@ -64,7 +64,7 @@ extern int NIO_IsServerSocketOpen(void);
extern int NIO_IsServerConnectable(NTP_Remote_Address *remote_addr);
/* Function to unwrap an NTP message from non-native transport (e.g. PTP) */
extern int NIO_UnwrapMessage(SCK_Message *message, int sock_fd);
extern int NIO_UnwrapMessage(SCK_Message *message, int sock_fd, double *net_correction);
/* Function to transmit a packet */
extern int NIO_SendPacket(NTP_Packet *packet, NTP_Remote_Address *remote_addr,

9
ntp_io_linux.c
View file

@ -559,7 +559,7 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family,
int l2_length)
{
double rx_correction, ts_delay, local_err;
double rx_correction = 0.0, ts_delay, local_err;
struct timespec ts;
poll_phc(iface, &local_ts->ts);
@ -600,6 +600,10 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
local_ts->ts = ts;
local_ts->err = local_err;
local_ts->source = NTP_TS_HARDWARE;
local_ts->rx_duration = rx_correction;
/* Network correction needs to include the RX duration to avoid
asymmetric correction with asymmetric link speeds */
local_ts->net_correction = rx_correction;
}
/* ================================================== */
@ -723,6 +727,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
{
struct Interface *iface;
int is_tx, ts_if_index, l2_length;
double c;
is_tx = event == SCH_FILE_EXCEPTION;
iface = NULL;
@ -783,7 +788,7 @@ NIO_Linux_ProcessMessage(SCK_Message *message, NTP_Local_Address *local_addr,
return 1;
}
if (!NIO_UnwrapMessage(message, local_addr->sock_fd))
if (!NIO_UnwrapMessage(message, local_addr->sock_fd, &c))
return 1;
if (message->length < NTP_HEADER_LENGTH || message->length > sizeof (NTP_Packet))